This study aimed to develop the design method for evaluating the seismic coefficients of coastal parapet levees with regard to level-1 earthquakes. In order to examine the applicability of seismic design method by using structural frame analysis and acceleration response spectrum, seismic coefficients of various coastal levees were calculated by the proposed method and seismic performance of the levees were verified.
It was clarified that the influence of the horizontal subgrade reaction on the footing and the configuration of steel pipe piles is relatively small on the horizontal seismic coefficients although the natural frequencies calculated by the frame analysis vary depending on the subgrade reaction and the configulation of piles.
Seismic performance verification was performed on pile stress of the pile foundation parapet levees and forces for the overturning and sliding of the spread foundation parapet levee. The stress-resistance ratio of piles decreased with the horizontal subgrade reaction on the footing, and increased as the diameter and plate thickness of the pile decreased. Considering the horizontal subgrade reaction on the footing increased the resistance-force ratio for sliding of the spread foundation levee and set it on the danger side, similar to the case of the pile foundation levees. Thus, it was recognized that safe side evaluation is obtained without the horizontal subgrade reaction on the footing.
Key Words: Coastal parapet levees, practical design, seismic coefficients, natural frequency, practical design